Overview

Until the 1990s, no one had evidence of planets around Sun-like stars anywhere in the universe, except for Earth and the other eight planets circling the Sun. Then in October 1995, Michel Mayor and Didier Queloz of the Geneva Observatory changed history. They located a planet orbiting 51 Pegasi, a star located just 40 light years away from Earth. Shortly thereafter, additional astronomers chimed in, announcing evidence for other extrasolar planets. The announcements triggered a great deal of excitement in the scientific community and among the public as well. The announcements finally brought confirmation that the nine planets within our solar system are not the only ones in the universe, and begged the question, "Is there life out there?"

Background

Astronomers had long suspected that Sun-like stars had orbiting planetary systems, but they never had data to back up their assumption. They...